In a UMTS (Universal Mobile Telecommunications System) network, attempts are made to optimize features of the system, which are based on W-CDMA (Wideband Code Division Multiple Access), by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), for the purposes of improving spectral efficiency and improving the data rates. In relationship to this UMTS network, long-term evolution (LTE) is under study for the purposes of further increasing high-speed data rates, providing low delay and so on (non-patent literature 1).
In a third-generation system, generally, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. Meanwhile, in an LTE system, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. Furthermore, in the UMTS network, successor systems of LTE are under study as well (for example, LTE-Advanced (LTE-A)), for the purpose of achieving further broadbandization and higher speed.